Dynamic Robot Model Implementation
I'm wondering if anyone can offer advice on how to approximate a non-rigid robot model. I'm implementing a model of a 3 DOF arm for a university independent study that uses a rollable prestressed tube (like this: http://www.youtube.com/watch?v=tJ5w8x... ) as one of the extensible elements (this is the robot: https://www.youtube.com/watch?v=xlHGN... ). Essentially it is just a rolled fiber composite that can be unrolled to provide a rigid tube like a tape measure. I can't model the roll because it deforms from its rigid form, but I can make the assumption that the boom section is rigid. I initially set the model up with a prismatic joint so the boom could slide in an out of the arm, but the arm then retracts into the body of the arm and eventually out the back and looks terrible. This method also introduces problems with collision checking in moveit due to self collisions when the boom extends into the arm, and with the environment when it extends out the back.
The next approach I'm researching is to dynamically set the length of the straight tube in the boom section so that the model renders properly within rviz/gazebo, dynamically resizes the collision elements, and correctly publishes transforms and link/joint states. I think I have a good handle publishing the transforms and states with a custom robot state publisher (I'm working on an implementation based on the tutorial: http://wiki.ros.org/urdf/Tutorials/Us... ) but I'm getting bogged down in the implementation details trying to work out how to update the collision and visualization meshes
There are 3 possibilities that seem feasible:
Publish the link as a marker with the transforms in a robot state publisher and skip the link in the urdf file that rviz parses so that the marker just fills in for the boom.
Modify a rviz node to update the representation of the mesh for the tube by subscribing to a robot state publisher along the lines of the answer to this thread: http://answers.ros.org/question/9425/... I'm still trying to understand how exactly rviz displays the model, but I assume it can be done programatically similar to gazebo.
It seems like a pointer to a robot model is passed around in gazebo, if this is also true in rviz it might be possible to subscribe to the pointer to the model in my state publisher, build the new model and switch it out with the old one. I'm not sure how to deal with race conditions that would be caused here without modifying rviz.
Does anyone have a better idea for how this could be done? Do any of the ideas I have so far seem like they are the right way to go?
